SLMs are used in many applications, two of which are display systems and printing systems. SLMs are increasingly being used because they have the benefit of high resolution while consuming lower power and less bulk than conventional Cathode Ray Tube technology. Examples of two well known SLM devices include Liquid Crystal Displays (LCDs) and Digital Micromirror Devices (DMDs). The SLM will typically consist of an array of picture elements, or pixels, which modulates light according to a spatial pattern on the device.
Generally, an LCD system used in projection systems consists of three LCD panels in which the primary colors, red, green, and blue, are combined from the three panels to form the desired image. An LCD panel consists of a liquid crystal material sandwiched between transmissive layers and divided into an array of individual picture elements. Each picture element can individually have an electric signal applied that causes the material to align in predictable ways. Light is passed to the panels and individual picture elements either allow the light to pass through or block the light. By modulating the opening and closing of the picture elements, an image is produced which is then directly viewed or projected on to the image plane or display plane through a display lens. Traditionally, the array is aligned with the horizontal and vertical axes.
Another version of an LCD system is known as Liquid Crystal on Silicon, which combines some of the features of an LCD panel with a DMD device. An LCD type device is placed over a reflective surface and the individual picture element either allows light to pass to the reflective surface or light is blocked from the reflective surface. The reflected light corresponding to the picture element is passed through the imaging system, usually combining three separate color images of red, green, and blue to the display plane.
DMDs are micromechanical devices that typically include an array of small reflective surfaces, or mirrors, on a semiconductor wafer to which an electrical signal is applied to deflect the mirror and change the reflected light applied to the device. A DMD-based system is created by projecting a beam of light to the device and selectively altering individual micro-mirrors with image data, and directly viewing or projecting the selected reflected portions to an image plane such as a display screen or printing surface. Each individual micromirror is addressable by an electronic signal and makes up one “display element” of the DMD. In many contexts, a single pixel of a DMD or other SLM device corresponds with a single image pixel in a projection display or printing context, but there are other ways to address the SLM device in order to comprise a pixel element of more than or less than a single SLM device pixel.
Further, techniques are sometimes desired for dithering of the displayed or printed images are provided in the art so that jagged lines, screen-door effects, temporal anomalies, and other discontinuities and undesirable image effects are reduced.